70 BRITISH FOSSIL CORALS. 
CHAPTER VII. 
CORALS FROM THE LOWER GREENSAND. 
‘Tur remains of true Polypi are very rare in this part of the British geological strata ; 
the fossil which Mr. Lonsdale has lately described under the name of Choristopetalum impar,' 
and which was found in the lower greensand at Atherfield, does not appear to us to 
belong to this class, and is, in our opinion, a Bryozoon. We have as yet met with but 
one species of Zoantharia, which can be referred with any degree of certainty to this 
formation. 
Family STAURID/ (p. Ixiv). 
Genus Houocystis (p. lxiv). 
Hotocystis rLecans. ‘Tab. X, fig. 5, 5a, 5 4. 
AstreA, Fitton, On the Strata below the Chalk, in Geol. Trans., s. 2, vol. iv, p. 352, 1843. 
ASTREA ELEGANS, Fitton, in Quarterly Journ. Geol. Soc., vol. ii, p. 296, 1847. 
CyatHoruora (?) ELEGANS, Lonsdale, Proceed. of the Geol. Soc., vol. v, part i, p. 83, tab. iv, 
fig. 12, 15, 1849. 
Corallum complex, astreiform, constituting a convex mass, and augmenting by extra 
calicular gemmation ; the young individuals being produced at the point of junction of the 
surrounding calices. Cora/lites somewhat prismatic, and cemented together laterally, 
either by the direct union of their walls, or by means of the coste, which are thick, and in 
general pretty well developed.  Ca/ices subpolygonal, separated in general by a simple but 
thick mural ridge ; sometimes by walls that remain distinct, and are in their turn separated 
by a small intermural furrow. Mossula deep. Colwmella very small, and appearing to be 
styliform. Septa forming three complete cycla, and four well-characterised systems. The 
four primary ones much more developed than the others, reaching almost to the centre of 
the fossula, and giving to the calice a crucial character, which is never met with in Astreide, 
Oculinide, Turbinolide, &. The septa are slightly exsert, closely set, thick exteriorly, 
and very slightly granulated laterally; they appear to have undivided edges, and they 
differ much in size, according to the cycla to which they belong. The interseptal dissepiments 
are simple, horizontal, or slightly convex, and placed at the same level in the different loculi, 
1 Proceedings of the Geol. Soc.. vol. vy, part i, p. 69, tab. iv, figs. 5 to 11, 1849. 
